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Birdsong and Other Animal Models for Human Speech, Song, and Vocal Learning

Birdsong and Other Animal Models for Human Speech, Song, and Vocal Learning

W. Tecumseh Fitch

Erich D. Jams

Publisher:

The MIT Press

DOI:10.7551/mitpress/9780262018104.003.0020

This chapter highlights the similarities and differences between learned song, in birds and other animal models, and speech and song in humans, by reviewing the comparative biology of birdsong and human speech from behavioral, biological, phylogenetic, and mechanistic perspectives. Our thesis is that song-learning birds and humans have evolved similar, although not identical, vocal communication behaviors due to shared deep homologies in nonvocal brain pathways and associated genes from which the vocal pathways are derived. The convergent behaviors include complex vocal learning, critical periods of vocal learning, dependence on auditory feedback to develop and maintain learned vocalizations, and rudimentary features for vocal syntax and phonology. The associated neural substrate is a set of specialized forebrain pathways found only in humans and other complex vocal learners, and it consists of premotor and motor forebrain systems that directly control brainstem vocal motor neurons. To develop and maintain function of the novel vocal-learning pathways, we argue that convergent molecular changes occurred on some of the same genes, including FoxP2 and axon guidance molecules. Our hypothesis is that the unique parts of the brain pathways, which control spoken language in humans and song in distantly related song-learning birds, evolved as specializations of a deeply homologous, preexisting motor system, which was inherited from their common ancestor and which controls movement and complex motor learning. The lesson learned from this analysis is that by studying the comparative behavioral neurobiology of human and nonhuman vocal-learning species, greater insight can be gained into the evolution and mechanisms of spoken language than by studying humans alone or humans only in relation to nonhuman primates. Published in the Strungmann Forum Reports Series.

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PRINTED FROM MIT PRESS SCHOLARSHIP ONLINE (www.mitpress.universitypressscholarship.com). (c) Copyright The MIT Press, 2017. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a monograph in MITSO for personal use (for details see http://www.mitpress.universitypressscholarship.com/page/privacy-policy).date: 19 March 2018